A light-driven photoelectrochemical sensor for highly selective detection of hydroquinone based on type-II heterojunction formed by carbon nanotubes immobilized in 3D honeycomb CdS/SnS2

Square-shaped Cu2MoS4 loaded on three-dimensional flower-like AgBiS2 to form S-scheme heterojunction as a light-driven photoelectrochemical sensor for efficient detection of serotonin in biological samples

Serotonin (5-HT) is a crucial neurotransmitter in the body, with its levels being particularly significant for life safety. Here, we designed the AgBiS2/Cu2MoS4 S-scheme heterojunction by uniformly immobilizing lamellar Cu2MoS4 on the surface of three-dimensional (3D) flower-like AgBiS2 using a simple physical mixing technique. In this case, AgBiS2 and Cu2MoS4 are bonded together by electrostatic attraction to form an active surface with a large specific surface area. Subsequently, the detector 5-HT bound to AgBiS2/Cu2MoS4/GCE undergoes hole oxidation and the photocurrent signal increases significantly. Meanwhile, the reaction mechanism of AgBiS2/Cu2MoS4 composite material was investigated through density functional theory calculations. The AgBiS2/Cu2MoS4/GCE sensor demonstrates a low detection limit of 0.046 nM and a wide linear range (0.0001-8 μM). Furthermore, by comparing UV-Vis spectrophotometry and fluorescence spectroscopy for the detection of 5-HT in human serum, it was proved that the sensor has an impressive recovery rate.

Strain redistribution for achieving wide-range and high-sensitivity monitoring of natural rubber-based sensors

Strain sensors with high sensitivity and wide detection range are essential for meeting diverse applications, such as precisely monitoring the movement of patients with bone defects during rehabilitation. However, extending the sensing range without compromising sensitivity, particularly for small strains, remains a significant challenge for flexible sensors. Here, a strain redistribution strategy was employed to achieve wide-range and high-sensitivity monitoring of natural rubber (NR)-based sensors. A rectangular NR-based sensor was initially developed using the swelling-infiltration method, demonstrating a broad strain range but low sensitivity. The introduction of V-notches on both sides of the sensor resulted in significant local strain enhancement, substantially improving sensitivity but significantly reducing the sensing range. For example, the gauge factor (GF) increased from 4.2 to 28.4 at 20 % strain, while the sensing range decreased from 400.5 % to 71.4 %. Furthermore, O-notches were integrated into the NR-based sensor to facilitate strain redistribution. A well-designed O-notch enhanced the sensing range by 40 % without sacrificing small-strain sensitivity. Additionally, the NR-based sensor with strain redistribution demonstrated a low detection limit (0.1 %), excellent cyclic stability, and biocompatibility, making it highly effective for detecting large and small deformations in the human body.

Designing In2S3/FeVO4/CNT Photoelectrode for Enhanced Visible Light Driven Oxygen Evolution

The development of efficient and stable photoelectrodes is essential for the advancement of photoelectrochemical (PEC) water-splitting technologies, which hold promise for efficient oxygen evolution reaction (OER), necessary for sustainable hydrogen production. In this study, the synthesis of a ternary composite, In2 ${_2 }$ S3 ${_3 }$ /FeVO4 ${_4 }$ /CNT has been reported, designed for highly efficient PEC oxygen evolution. The formation of In2 ${_2 }$ S3 ${_3 }$ /FeVO4 ${_4 }$ heterostructure enhances PEC performance significantly due to the type-II band alignment, which minimizes electron-hole recombination and improves charge separation. The addition of CNTs further enhances performance by providing conductive pathways that improve electron transport and reduce charge transfer resistance. The resulting In2 ${_2 }$ S3 ${_3 }$ /FeVO4 ${_4 }$ /CNT ternary composite achieves a current density of 14.70 mAcm- 2 ${^{ - 2} }$ at 1.8 V vs. RHE, representing a notable increase in performance. Electrochemical impedance spectroscopy (EIS) shows that the ternary composite has the lowest charge transfer resistance, while Bode phase analysis indicates a longer carrier lifetime, emphasizing the synergistic effect of heterostructure formation and CNT inclusion. The ternary composite also demonstrates excellent stability and responsiveness during transient photocurrent cycling, maintaining performance under repeated chronoamperometric ON/OFF cycles, making it a strong candidate for water-splitting applications driven by visible light.

Construction of a In2O3/ultrathin g-C3N4 S-scheme heterojunction for sensitive photoelectrochemical aptasensing of diazinon

A single semiconductor-based photoelectrochemical (PEC) aptasensor usually faces a challenge of low sensitivity due to poor solar energy utilization and a high photogenerated carrier recombination rate. Herein, an ultra-thin carbon nitride nanosheet-coated In2O3 (In2O3/CNS) S-type heterojunction-based PEC aptasensor has been established to achieve highly sensitive detection of diazinon (DZN) pesticide in water environment. Construction of S-type heterojunction induces a band shift and an electric field effect, enhancing light utilization and accelerating directional transmission of carriers, leading to outstanding PEC performance. The creation of internal electric field at interface ensures stable carrier transport. Additionally, ultrathin CNS structure can effectively shorten the transport path of carriers. The close coating of In2O3 and CNS promotes the transfer of charge. The synergistic effects amplify the sensor's response, ultimately enabling the effective detection of DZN residue over a wide detection range (0.98 ∼ 980.0 pg mL-1), a low detection limit (0.33 pg mL-1, S/N = 3) and excellent accuracy in practical application (RSD < 5 %). This work provides a reference for the construction of a new S-type heterojunction-based PEC sensor.

Enriching Oxidation Sites-Based Facets in Lead Chromate to Boost Photoelectrochemical Sensing Response

A key issue in photoelectrochemical applications is the modification of the behavior of photogenerated charge barriers. An effective strategy to improve the photoelectrochemical performance of semiconductor materials is to use the facet effect to promote spatial charge separation. In this work, three different morphologies of lead chromate (PbCrO4) crystals are prepared by a simple hydrothermal method that used ammonium fluoride as the structure-directing agents. Spatial separation of photogenerated electrons and holes is clearly demonstrated in the (012), (020), and (200) facets of PbCrO4 crystals. In situ photo-deposition experiments reveal that the oxidation and reduction sites are distributed on the anisotropic (012) and (020)/(200) facets of all the PbCrO4 crystals. PbCrO4 synthesized with a high Pb2+/F- ratio with maximum exposure of (012) facet has remarkably better performance in photoelectrochemical detection of ascorbic acid compared with PbCrO4 synthesized either without ammonium fluoride or with a low Pb2+/F- ratio. The photoelectrochemical detection performance correlates well with the surface photovoltage difference between the anisotropic facets. The study provides fundamental understanding of the facet-dependent activity of PbCrO4 crystals, which will be beneficial for advancing understanding of spatial charge separation in semiconductor-based photoelectrochemical applications.

Direct photoelectrochemical detection of ethanol in complex biological sample

The development of advanced photoelectrochemical (PEC) technology for the direct detection of ethanol in complex biological sample, has become a hot topic. However, the photo-active nanomaterials, which could generate the photo-induced carriers under illumination, are susceptible to biofouling and interference in complex bio-matrices. In this work, the silica nanochannel-protected TiO2 nanomaterials was reported for the first time that enables the direct sensing of ethanol in real fruits and untreated whole blood. The modification of SNC enhanced the sensitivity of ethanol detection by promoting light absorption, electron-hole separation, and surface reaction rate of photo-active materials. Meanwhile, the biofouling macromolecules and interference signals can be effectively excluded due to the hydrophilic properties, size, and electrostatic exclusion of nanochannels. As a result, without any complex sample pretreatments, the proposed PEC sensor can be directly immersed in complex biological samples for ethanol detection, exhibiting a broad linear range (1.775 μM-20 mM) and a low detection limit (1.2 μM), as well as excellent reproducibility and stability. This work paves a new path for PEC sensors in real biomedical applications.

Molecularly imprinted photoelectrochemical sensor for ultrasensitive and selective detection of hydroquinone using 0D CdS nanoparticle/3D flower-like ZnIn2S4 microsphere nanocomposite

A novel photoelectrochemical (PEC) sensor was developed for the ultra-sensitive and highly selective detection of hydroquinone (HQ), featuring a composite structure that combines 0D CdS nanoparticles with a 3D flower-like ZnIn2S4 microsphere. The sensor, termed rMIP/CdS/ZnIn2S4, employed molecularly imprinted polymers (MIPs) to achieve specific recognition of HQ. An p-phenylenediamine (pPD) polymer film was electrochemically polymerized onto the surface of the CdS/ZnIn2S4 composite-coated glassy carbon electrode (GCE). Through hydrogen bonding, HQ molecules were imprinted onto the polymer film. Subsequent elution removed these molecules, leaving behind specific recognition sites, enabling selective detection of HQ. The unique spatial structure and heterojunction properties of the 0D CdS nanoparticle/3D flower-like ZnIn2S4 composite, combined with molecular imprinting, significantly enhanced the photocurrent response and increased the selectivity and sensitivity for HQ detection. Under optimal conditions, the rMIP/CdS/ZnIn2S4 sensor demonstrated a low detection limit (0.7 nmol·L-1, S/N=3) over a wide linear range of 1-1200 nmol·L-1. The sensor was successfully applied to detect HQ in real water samples, showing promise for environmental pollution control applications.

Metal organic framework-derived CuO/Cu2O polyhedron-CdS quantum dots double Z-scheme heterostructure for cathodic photoelectrochemical detection of Hg2+ in food and environment

This study employed an innovative copper oxide/cuprous oxide (CuO/Cu2O) polyhedron‑cadmium sulphide quantum dots (CdS QDs) double Z-scheme heterostructure as a matrix for the cathodic PEC determination of mercury ions (Hg2+). First, the CuO/Cu2O polyhedral composite was prepared by calcining a copper-based metal organic framework (Cu-MOF). Subsequently, the amino-modified CuO/Cu2O was integrated with mercaptopropionic acid (MPA)-capped CdS QDs to form a CuO/Cu2O polyhedron-CdS QDs double Z-scheme heterostructure, producing a strong cathodic photocurrent. Importantly, this heterostructure exhibited a specifically reduced photocurrent for Hg2+ when using CdS QDs as Hg2+-recognition probe. This was attributed to the extreme destruction of the double Z-scheme heterostructure and the in situ formation of the CuO/Cu2O-CdS/HgS heterostructure. Besides, p-type HgS competed with the matrix for electron acceptors, further decreasing the photocurrent. Consequently, Hg2+ was sensitively assayed, with a low detection limit (0.11 pM). The as-prepared PEC sensor was also used to analyse Hg2+ in food and the environment.

In-situ synthesized MgIn2S4/CdWO4 type-II heterojunction as a light-driven photoelectrochemical sensor for ultrasensitive detection of catechol in environmental water samples

As an essential chemical intermediate, catechol (CC) residues may have adverse effects on human health. Herein, an effective and facile photoelectrochemical sensor platform based on MgIn2S4/CdWO4 composite is constructed for monitoring CC. MgIn2S4 increases light absorption range and activity, while CdWO4 enhances photoelectronic stability, and the type-II heterojunction formed can significantly enhance photocurrent response. Due to the autoxidation process, CC is converted into oligomeric products, which increase the spatial site resistance and attenuate the overall photocurrent response. It is worth noting that the cauliflower-like structure of MgIn2S4 can provide a large specific surface area, and the presence of Mg2+ promotes autoxidation, thus providing a suitable condition for detecting CC. Under optimal conditions, the MgIn2S4/CdWO4/GCE photoelectrochemical sensor has a prominent linear relationship in the range of CC concentration from 2 nM to 7 μM, with a limit of detection of 0.27 nM. With satisfactory selectivity, excellent stability, and remarkable reproducibility, this sensor provides a crucial reference value for effectively and rapidly detecting pollutants in environmental water samples.

Red and near-infrared light-activated photoelectrochemical nanobiosensors for biomedical target detection

Photoelectrochemical (PEC) nanobiosensors integrate molecular (bio)recognition elements with semiconductor/plasmonic photoactive nanomaterials to produce measurable signals after light-induced reactions. Recent advancements in PEC nanobiosensors, using light-matter interactions, have significantly improved sensitivity, specificity, and signal-to-noise ratio in detecting (bio)analytes. Tunable nanomaterials activated by a wide spectral radiation window coupled to electrochemical transduction platforms have further improved detection by stabilizing and amplifying electrical signals. This work reviews PEC biosensors based on nanomaterials like metal oxides, carbon nitrides, quantum dots, and transition metal chalcogenides (TMCs), showing their superior optoelectronic properties and analytical performance for the detection of clinically relevant biomarkers. Furthermore, it highlights the innovative role of red light and NIR-activated PEC nanobiosensors in enhancing charge transfer processes, protecting them from biomolecule photodamage in vitro and in vivo applications. Overall, advances in PEC detection systems have the potential to revolutionize rapid and accurate measurements in clinical diagnostic applications. Their integration into miniaturized devices also supports the development of portable, easy-to-use diagnostic tools, facilitating point-of-care (POC) testing solutions and real-time monitoring.

Carbon-based photoelectrochemical sensors: recent developments and future prospects

Owing to the considerable potential of photoelectrochemical (PEC) sensors, they have gained significant attention in the analysis of biological, environmental, and food markers. However, the limited charge mass transfer efficiency and rapid recombination of electron hole pairs have become obstacles in the development of PEC sensors. In this case, considering the unique advantages of carbon-based materials, they can be used as photosensitizers, supporting materials and conductive substrates and coupled with semiconductors to prepare composite materials, solving the above problems. In addition, there are many types of carbon materials, which can have semiconductor properties and form heterojunctions after coupling with semiconductors, effectively promoting the separation of electron hole pairs. Herein, we aimed to provide a comprehensive analysis of reports on carbon-based PEC sensors by introducing their research and application status and discussing future development trends in this field. In particular, the types and performance improvement strategies of carbon-based electrodes and the working principles of carbon-based PEC sensors are explained. Furthermore, the applications of carbon-based photoelectric sensors in environmental monitoring, biomedicine, and food detection are highlighted. Finally, the current limitations in the research on carbon-based PEC sensors are emphasized and the need to enhance the sensitivity and selectivity through material modification, structural design, improved device performance, and other strategies are emphasized.

Remediation of phenanthrene by highly efficient CdS-SnS photocatalyst and its cytotoxic assessments

Cadmium sulfide-tin sulfide (CdS-SnS) nanoparticles are a novel kind of photocatalyst. These CdS-SnS nanoparticles are synthesized and characterized using UV-Vis, FT-IR, XRD, SEM-EDX, and DLS techniques, to understand their size distribution, crystalline nature, morphology, shape, optical properties, and elemental composition. This research offers insight into the efficient photocatalytic degradation of Phenanthrene (PHE) using CdS-SnS. The CdS-SnS NPs as photocatalyst can effectively photodegrade the polycyclic aromatic hydrocarbons (PAH) such as phenanthrene under simulated solar and UV light. UV-vis spectra of these nanoparticles exhibit peaks at 365 and 546 cm-1 respectively, the mean size of the CdS-SnS NPs in DLS is determined to be 78 nm. The CdS-SnS stretching frequency was observed at wave numbers below 700 cm-1, the absorption peak at 1123 cm-1 indicates the presence of C-N stretch or CS bond of thiourea, while the peak at 1350.38 cm-1 corresponds to the tris-amine C-N stretch in FT-IR. Additionally, the peaks observed at 2026 cm-1 indicate the presence of isothiocyanate (NCS). 1456.23 cm-1 represents the asymmetric scissor deformation vibration. EDAX revealed the presence of elemental Cd and Sn oxides. The antimicrobial studies showed that the CdS-SnS NPs at the concentration of 150 μg/mL, exhibit maximum inhibition (15 ± 1.25 mm) against the strains Proteus mirabilis followed by Staphylococcus epidermidis and Clostridium spp. Among fungal strains Colletotrichum spp. exhibits the maximum zone of inhibition (9 ± 0.25). This research also observed the cytotoxic effects of CdS-SnS NPs on HepG2 and ZF4 cells. HepG2 cells exhibited 50% inhibition at 50 μg/mL and 70% inhibition at 100 μg/mL concentrations, while ZF4 cells exhibited 50% inhibition at 50 μg/mL and 78% inhibition at 100 μg/mL concentrations, respectively. The parameters like concentration of PHE, concentration of CdS-SnS NPs, pH, and sources of irradiation on batch adsorption were examined to maximize the efficiency of the photodegradation process.

Sulfur vacancy-rich (α/β-CdS)/SiO2 photocatalysts for enhanced visible-light-driven photocatalytic degradation of rhodamine B

The development of highly efficient photocatalysts for visible-light-driven degradation of organic pollution is of great interest for wastewater purification. In this work, a sulfur vacancy-rich (α/β-CdS)/SiO2 (α: hexagonal & β: cubic) photocatalyst with a high catalytic activity was novelly synthesized on a nano-SiO2 carrier by the reaction of Cd2+ with a CS2 storage material (CS2SM) as sulfur source and crystalline modifiers. The dispersion of α/β-CdS on the nano-SiO2 carrier significantly enhanced the visible-light-driven catalytic activity of (α/β-CdS)/SiO2 photocatalyst, and 93.37 % rhodamine B (RhB) conversion was determined over 50 mg (α/β-CdS)/SiO2 photocatalyst for 30 mL 400 mg/L RhB solution at light intensity of 150 mW/cm2 and 298.15 K. After five cycle tests, the (α/β-CdS)/SiO2 photocatalyst still owned excellent visible-light-driven catalytic degradation stability (>90 %). The characterizations of morphology, functional groups, and photo-electrochemistry of (α/β-CdS)/SiO2 photocatalyst demonstrated that nano-SiO2 as a carrier played meaningful role in dispersing α/β-CdS and reducing agglomeration, thus increasing the active site of photocatalytic degradation reaction, and the presence of α/β hetero-phase junctions and sulfur vacancies allows the rapid separation of photo-generated carriers and inhibits photo-generated electron-holes recombination. Meanwhile, the electron paramagnetic resonance (EPR) and free radical masking test have also proved that the main active species is ·O2- for the oxidation of RhB. Therefore, the work is providing a new reference to the visible-light-driven degradation of wastewater with high RhB concentration at room temperature.